First Report of Heterobasidion annosum on Pinus pinaster in Spain

Abstract

The basidiomycete Heterobasidion annosum (Fr.) Bref. (=Fomes annosus (Fr.) Cooke), one of the most important pathogens in coniferous forests in Europe, Asia, and North America, causes root and butt rot. H. annosum was first recorded on Pinus pinaster Ait. (commonly known as Maritime pine) in France and Great Britain in 1961 (4) and Portugal in 1986 (2). P. pinaster is the most widespread conifer in Spain, with more than 700,000 and 600,000 ha in pure and mixed stands, respectively. Over the last few years, P. pinaster decline was observed in several stands in the center of the Iberian Peninsula. Unusual crown transparency, small needles, foliage discoloration, and early tree death are characteristic decline symptoms associated with the high mortality rate on this species. In June of 2010, 11 trees (40 to 60 years old) with a different degree of decline were felled in two zones (42°2′41″N, 3°18′14″W, elevation 1,096 m and 41°55′40″N, 3°12′3″W, elevation 1,128 m) and cut into sections (stump height, breast height, and near the top). Wood slices were removed from each section and taken to the laboratory. Samples were placed in moist chambers with optimal conditions of humidity and temperature to enhance pathogen growth. After 20 days of incubation in darkness at 25°C, H. annosum (anamorph Spiniger meineckellum [A. Olson] Stalpers) occurred on most of these slices. Conidiophores with subglobose to pyriform conidia (5.8 × 4.2 μm) were observed with a compound microscope. The fungus was isolated to extract DNA by disruption of the mycelium followed by washes with phenol/chloroform/isoamyl alcohol solution (25:24:1). DNA was precipitated with 20% polyethylene glycol solution. PCR was carried out according to the instructions of the manufacturer of Dynazyme II DNA polymerase (Finnzymes Ltd, Espoo, Finland) with ITS primers, 1F (5′-CTTGGTCATTTAGAGGAAGTAA-3′) and 4 (5′-TCCTCCGCTTATTGATATGC-3′). After DNA purification, samples were sequenced (SECUGEN, Madrid, Spain) and aligned and corrected with Geneious Pro 5.3 to obtain the consensus sequences. Resulting DNA sequences of two isolates were deposited in GenBank (Nos. FR850494 and FR850495), and compared with a Blastn search at GenBank showing 100% identity and 100% coverage with H. annosum sensu stricto, former ISG-P (intersterility group of pines). For pathogenicity tests, 10 seedlings (2 year old) were inoculated with autoclaved P. pinaster wood chips colonized by H. annosum, and 10 control seedlings were inoculated with noncolonized wood chips. Inoculums were prepared by growing H. annosum on 4-mm-diameter wood chips placed on potato dextrose agar media for 3 weeks. The wood chips were put inside an oblique incision made at 6 cm above the soil line and wrapped with Parafilm. After 8 weeks in a growth chamber at 22.5°C with a 14-h photoperiod, the inoculated seedlings showed typical symptoms and 3 seedlings of 10 were dead. H. annosum was previously recorded on P. sylvestris in central Spain (1), causing needle drop, swelling at the stump height, and presence of dead trees by circular areas. This pathogen was also reported on P. nigra in northeastern Spain, associated with defoliation and mortality (3). To our knowledge, this is the first record of H. annosum on P. pinaster in Spain. References: (1) J. Benito-Martínez. An. Jardín Bot. Madrid 3:23, 1943. (2) N. Neves et al. EPPO Bull. 16:505, 1986. (3) J. Oliva et al. Bol. Sanidad Vegetal. Plagas. 34:415, 2008. (4) P. Spaulding. US Dep. Agric. Agric. Handb. 197:100, 1961.

Ophiostomatoid fungi associated with declined Pinus pinaster stands in Spain

“…However, we should take into account the possibility that the present state of the decline may be due to a complex relationship between fungal (Ophiostoma minus, Heterobasidion annosum, recently detected in some areas close to our sampling plots (Prieto-Recio et al, 2012), or even other pathogens as Phytophthora cinnamomi...), soil, climatic and silvicultural factors. Anyway, further work is necessary to determine the pathogenicity of O. minus and other associated ophiostomatoids fungi on adult trees, with the aim to definitively establish the association of this fungus with the maritime pine decline.…”

Pathogenicity of Spanish isolates of Heterobasidion annosum s. s. in Pinus pinaster seedlings

“…The Spanish isolates of Heterobasidion used in the study (H1 and H4) were previously isolated and identified as H. annosum s. s. (Prieto-Recio et al 2012). The Spanish isolates of Heterobasidion used in the study (H1 and H4) were previously isolated and identified as H. annosum s. s. (Prieto-Recio et al 2012).…”

“…A total of 120 two-year-old P. pinaster seedlings (Meseta Castellana provenance, Spain) were obtained from a Government tree nursery in Castile and Leon. The Spanish isolates of Heterobasidion used in the study (H1 and H4) were previously isolated and identified as H. annosum s. s. (Prieto-Recio et al 2012). The sequences were deposited in the EMBL/GenBank database (GenBank Accession No.…”

“…Although H. annosum has occasionally been recorded on Pinus sylvestris and Pinus nigra in Spain, the presence of the fungus on P. pinaster in association with forest decline is a very recent finding (Prieto-Recio et al 2012). Bref.…”

“…In recent years, P. pinaster decline, characterized by unusual transparency at the crown, small needles, foliage discoloration and early tree death, has been observed in association with a high mortality rate in several forests in the centre of the Iberian Peninsula. Although H. annosum has occasionally been recorded on Pinus sylvestris and Pinus nigra in Spain, the presence of the fungus on P. pinaster in association with forest decline is a very recent finding (Prieto-Recio et al 2012). This pathogen is very aggressive on Pinaceae; however, some pine species such as P. pinea and P. halepensis have shown a lesser susceptibility (Scire et al 2011).…”